Tungsten carbide

[7] Tungsten carbide powder was first synthesized by H. Moissan in 1893, and the industrial production of the cemented form started 20 to 25 years later (between 1913 and 1918).

[16] Chemical vapor deposition methods that have been investigated include:[13] Solid tungsten carbide is prepared using techniques from powder metallurgy developed in the 1920s.

[7] The mixture is pressed, then sintered by heating it to temperatures of 1,400 °C (2,550 °F) to 1,600 °C (2,910 °F); the binder melts, wets, and partially dissolves the tungsten grains, binding them together.

The fine microstructure of this phase provides high hardness (2800–3500 HV) combined with good toughness when compared with other tungsten carbide compounds.

[25] Investigation of the phase diagram of the W-C-Co system shows that WC and Co form a pseudo binary eutectic.

[25] In the presence of a molten phase such as cobalt, abnormal grain growth is known to occur in the sintering of tungsten carbide, with this having significant effects on the performance of the product material.

[30][31] It has been found wear and oxidation properties of cemented carbide can be improved by replacing cobalt with iron aluminide.

In these applications it is also used for wear and corrosion resistant components in inlet control for well screens, sub-assemblies, seal rings and bushings common in oil and gas drilling.

[40] It is generally utilised as a button insert, mounted in a surrounding matrix of steel that forms the substance of the bit.

[citation needed] Tungsten carbide is also an effective neutron reflector and as such was used during early investigations into nuclear chain reactions, particularly for weapons.

A criticality accident occurred at Los Alamos National Laboratory on 21 August 1945 when Harry Daghlian accidentally dropped a tungsten carbide brick onto a plutonium sphere, known as the demon core, causing the subcritical mass to go supercritical with the reflected neutrons.

[citation needed] Sharpened carbide tipped spikes (known as studs) can be inserted into the drive tracks of snowmobiles.

The carbide tips and segments reduce wear encountered when the snowmobile must cross roads and other abrasive surfaces.

[46] Tungsten carbide may be used in farriery, the shoeing of horses, to improve traction on slippery surfaces such as roads or ice.

[48]: 73 Tungsten carbide is also used for making surgical instruments meant for open surgery (scissors, forceps, hemostats, blade-handles, etc.)

[52] Some consider this useful, since an impact would shatter a tungsten ring, quickly removing it, where precious metals would bend flat and require cutting.

[50] Special tools, such as locking pliers, may be required if such a ring must be removed quickly (e.g. due to medical emergency following a hand injury accompanied by swelling).

[53] Tungsten carbide is widely used to make the rotating ball in the tips of ballpoint pens that disperse ink during writing.

[58] The primary health risks associated with tungsten carbide relate to inhalation of dust, leading to silicosis-like pulmonary fibrosis.

Tungsten carbide inserts
Tungsten carbide inserts
α-Tungsten carbide in the unit cell
α-WC structure, carbon atoms are gray. [ 5 ]
Cemented carbide drill and end mills
A tricone roller cone assembly from a raiseboring reamer, showing the protruding tungsten carbide buttons inset into the rollers
A square base of metal blocks, with a smaller square of metal on the top in the center, a Cooper block (the "core") contained in its center. A ruler along one side of the base shows roughly 10.5 inches (270 mm) square.
A re-creation of the experiment involved in the 1945 demon core incident. The sphere of plutonium is surrounded by tungsten carbide blocks acting as neutron reflectors .
A Nokian bicycle tire with tungsten carbide spikes. The spikes are surrounded by aluminum.
Tungsten carbide ring
Spherical tungsten carbide under scanning electron microscope , magnification x950, Material Laboratory